Nutrient - A walnut-rich diet may help you fight against stress and lower your blood pressure

By Dr Pieris Nicola

According to an international team of nutritional scientists at Pennsylvania State University, the addition of walnuts and walnut oil to the daily diet may help the body cope better with stress, as well as lowering blood pressure.

A steady drumbeat of studies has shown that nuts really are a “genuine” health food. True, the fat content of nuts is relatively high, but the total amount of fat you eat is not linked with disease. What really matters is the type of fat consumed. Most of the fats present in nuts are “healthy” unsaturated fats, in contrast to the “bad” saturated fats found in red meat and full-fat dairy products. This favourable fatty acid profile may contribute to the benefits of nut consumption observed in studies, including a reduction in the risk of heart disease and type 2 diabetes, and improved levels of LDL (bad) and HDL (good) cholesterol.

In addition to being rich in unsaturated fats, nuts are an excellent source of health-promoting nutrients including fibre, vitamins and minerals, arginine-rich proteins, and numerous phytochemicals including carotenoids, phenols (phenolic acid, flavonoids, stilbenes), and phytosterols. Phytochemicals are plant chemicals with potent biological actions which may help in protecting against chronic disease, including antioxidant and anti-inflammatory activity as well as the capacity to reduce cell proliferation and lower LDL cholesterol.

Nuts also contain arginine, an amino acid used by the body to produce nitric oxide, a tiny molecule that helps relax blood vessels to allow blood to flow easily, keeps the lining of the blood vessels healthy, and reduces the risk of potentially dangerous blood clots.

According to leading nutritional and health experts, on a scale of overall nutritional quality, walnuts stand out as the nutritional superstars packing the most nutrient benefits in a nutshell.

Go nuts about walnuts

Walnuts (Juglans regia) are one of the oldest tree foods known to humans, with historical references dating back to Persia in 7000 BC. They are also one of the richest natural sources of plant antioxidants, ranking the highest of any of the tree nuts in their antioxidant activity, most of which can be attributed to their very high content of plant phenols.

Walnuts have a very unique nutrient profile because,unlike most nuts that are rich in the monounsaturated fatty acid oleic acid,walnuts contain significant amounts of polyunsaturated fatty acids, specifically alpha-linolenic acid (ALA), the plant form of omega-3 fatty acids.

ALA is an essential fat, which means the body requires it for normal functions, but is incapable of producing it. Hence it is necessary to acquire it from the food we eat. Scientific research suggests that ALA may help prevent clots, stabilise heart rhythms, maintain elasticity and flexibility of the arteries, and help lower levels of C-reactive protein, a marker for inflammation and strong predictor of cardiovascular disease risk.

And according to a recent study, walnuts may even help protect us against the detrimental effects of stress.

Cracking the problem of stress-induced high blood pressure

Our blood pressure rises during times of stress. However, studies suggest that an exaggerated blood pressure response to stress may be a risk factor for hypertension, coronary heart disease and stroke – some of the UK’s biggest killers.

In today’s fast paced world, it is difficult, and at times impossible, to avoid stress, so a dietary change that could help our bodies fight stress could potentially have far-reaching health benefits.

Sheila West, associate Professor of bio-behavioural health and nutritional sciences at Penn State University and study author, wanted to determine if walnuts and walnut oil (good sources of ALA) reduce blood pressure during stressful conditions.

Her team of researchers conducted a randomised, crossover study of 22 healthy adults with elevated LDL cholesterol levels. Participants were placed on one of three calorie-matched diets specifically designed so that no changes in weight occurred in any participant. The diets comprised of a standard American diet without nuts, a similar diet with 1.3 ounces of walnuts (9 whole walnuts) and a tablespoon of walnut oil substituted for some of the bad fat in the average American diet, and a third diet including walnuts, walnut oil and 1.5 tablespoons of flax seed oil. The walnuts, walnut oil, and flaxseed oil were either mixed into the participants’ food or eaten as a snack.

Each participant was expected to consume all three of the diets, in random order, for a period of six weeks each with a one-week break in between. Everything the participants ate during the six-week diet periods were provided for.

At the end of each diet, participants had their stress levels raised in two ways: by being asked to prepare and present a three-minute speech and by having one foot submerged in ice-cold water. During both tests, researchers took blood pressure readings from the participants.

The researchers found that including walnuts and walnut oil in the diet not only reduced LDL levels but also lowered both resting blood pressure and most surprisingly blood pressure during stress. The exact mechanism leading to these changes is unknown, but walnuts are a rich source of bioactive substances, including ALA, which could be responsible for the beneficial effects on blood pressure.

Additionally, researchers found that when the study participants consumed flax seed oil (a richer source of ALA) in addition to the walnuts, they showed significant improvements on a separate measure of vascular health, and also demonstrated a reduction in C-reactive protein levels and therefore inflammation in the body, a prominent cardiovascular disease risk factor.

Professor West commented: “This is the first study to show that walnuts and walnut oil reduce blood pressure during stress.”

The study findings were reported in the Journal of the American College of Nutrition.

Walnuts are a whole food with a wide range of potential health benefits. And the good news is that you can make room for this highly nutritious food without feeling guilty about your weight because studies have found no significant association between eating walnuts and weight gain.

So consider going nuts and making walnuts a regular part of a balanced, healthful diet. They really are all they are cracked up to be, and more!

Article References

News release, Pennsylvania State University. West S et al. Journal of the American College of Nutrition, October 2010.